Field of the Invention
The present invention relates to a differential device which is provided in a vehicle such as, for example, an automobile.
Description of the Related Art
Japanese Utility Model Registration No. 2606235 has made known a conventional differential device in which a washer is interposed between a back surface of a tooth portion of each of output gears and an input member (for example, a differential case) and an oil groove guiding lubricant oil is provided in a recess shape in a surface of the input member facing the back surface of each output gear.
In the conventional device, on the surface of the input member facing the back surface of each output gear, particularly on a region part of said surface of the input member, which is located on a back surface side of a meshing portion between the output gear and a differential gear, large thrust reaction force acts from the meshing portion via the tooth portion of the output gear and the washer.
In spite of the above situation, an oil groove in the conventional device is formed in the region part located on the back surface side of the meshing portion in the surface of the input member facing the back surface of the output gear, namely, the region part on which the large thrust reaction force acts. This may cause a decrease in support rigidity of the region part which needs to bear large load burden, so that durability of the region part, accordingly durability of the input member may deteriorate. In addition, due to concentration of the load on an edge portion of the oil groove, the durability of the input member may deteriorate.
Furthermore, such problems may arise more seriously in a differential device whose input member, in particular, is required to be reduced in thickness and weight, such as a differential device which is made thinner in an axial direction of the output gears of the differential device by making the diameter of the output gears sufficiently larger than that of the differential gears such that the output gears can have a sufficiently larger number of teeth than that of the differential gears.